Such devices, which are attachable to the body of a test subject, are for example known as so-called pedometers; during the running or walking motion of the test subject, acceleration forces arising on the body are recorded via an acceleration sensor of the pedometer attached to the body and the number of steps completed is counted. The number of steps so determined is a measure of the physical activity of the test subject. Such pedometers are used for sport or fun and have only a unidimensional accelerator sensor for recording accelerations in a vertical direction.
Such a device, however, can only be used to a limited extent in the field of clinical medicine for determination of the degree of physical disability of patients, in particular of patients suffering from multiple sclerosis (hereinafter abbreviated to MS patients), since with this state of the art only dynamic types of motion, such as walking and jogging, can be recorded in an undifferentiated way, while in the case of MS patients with a more severe degree of disability continuous walking or jogging is only possible to a limited extent, or not possible at all, and the types of motion are limited to static states such as lying, sitting and standing, as can be seen from Table 1 below, which shows the so-called “Hauser Ambulation Index” for medical classification of multiple sclerosis patients, with the scale of this index extending from Level 0 to 9. Low values correspond to no or only slight disability, whereas high values correspond to a greater degree of disability.
TABLE 10No symptoms, fully active1Normal walking behaviour, but the patient reportsdisability in sports and other demanding activities2Unusual gait or occasionally disturbed equilibrium;the unusual gait is noticed by relatives and friends,takes not more than 10 s for 8 m3Can walk unaided, takes not more than 20 s for 8 m4Needs support on one side (crutch or stick),takes not more than 20 s for 8 m5Needs support on both sides (crutches, sticks orwalking aid) and takes more than 20 s for 8 m6Needs support on both sides and takes more than20 s for 8 m, can sometimes use a wheelchair7Walking is limited to a few steps with support onboth sides, can no longer walk 8 m, can use thewheelchair for most activities8Confined to the wheelchair, can still move ithim/herself9Confined to the wheelchair, can no longer move ithim/herself
Apart from the “Hauser Ambulation Index” summarized in Table 1, there are also other measurement systems for grading or classification of the degree of disability of MS patients. The EDSS (Expanded Disability Status Scale) can be cited here merely as an example. The existence of several such independent classification systems already shows the weaknesses of such a classification, which are due to subjectivity.
At the present time, admission as an inpatient of the attending physician is required in order to continuously monitor whether and to what extent a treatment prescribed for an MS patient is leading to an improvement or a deterioration in the state of health. During each of these regular periods of admission as an inpatient a medical examination is carried out and on this basis a degree of disability is assigned to the patient, the result of the examination being naturally dependent on the momentary state of mind of the patient and also of the examining physician (being in particular also influenced by the so-called “doctor in a white coat” effect) and thus not dependent on objectivizable criteria. The assessment of the efficacy of medication used in MS therapy is therefore not subject to objectivizable criteria, with the consequence that the direction of therapy followed cannot be corrected early enough.
The examination and classification of the degree of disability or of the activity of patients are of particular importance in the development of drugs and in clinical studies to check their efficacy. Naturally, in the course of medication with a drug to be tested, the degree of physical disability is checked at particular intervals. Because of the above-mentioned range of variation in the measurement results obtained in this process, a proper assessment of efficacy is almost impossible at the present time.